This invention relates to apparatus for controlling antenna rotators and more particularly to apparatus especially suited for controlling antenna rotators which are used to frequently change the antenna heading.
Antenna rotators and controllers are widely used for applications, such as amateur radio, where the antenna heading needs to be changed frequently, conveniently and reliably. Typical of antenna rotators and controllers are those available under the trade designations Ham and Tailtwister from Cornell-Dubilier Electronics Division of Federal Pacific Electric Company of Fuguay-Varina, N.C. Such rotator units each include a potentiometer for sensing the angular position of the upper rotator housing (to which is mounted the antenna), a brake system including a solenoid-operated wedge and sixty equally spaced grooves cast into the lower housing of the rotator to receive the wedge, a motor for rotating an antenna clockwise or counterclockwise; and a pair of limit switches for sensing when the upper housing nears the 0 degree and 360 degree angle positions. The controller for this rotator includes a brake release switch, a clockwise rotation switch, a counterclockwise rotation switch, and an analog panel meter for visually displaying the antenna heading. While the brake release switch is held closed by the operator, the brake solenoid is energized which, absent binding, disengages the brake. To rotate the antenna using this type controller, the operator must first depress and hold the brake release switch to release the brake, and then depress and hold the desired one of the rotation switches. When the desired rotation is nearly complete, as displayed on the analog panel meter, the depressed rotation switch is released and the antenna is allowed to "coast" to a stop. Once the antenna stops, the brake release switch is released to engage the brake.
Several problems arise in use of controllers such as the Cornell-Dubilier controllers described above. The operator's attention and simultaneous manual actuation of two switches is required for the entire time the rotator is turning with such controllers. With large antenna systems, inadvertently releasing the brake release switch while the antenna is still in motion can damage the brake, the antenna, or the tower. The motor in rotator systems with such controllers is either fully on or fully off, which causes large forces to be applied to the tower and antenna when starting and stopping rotation. Under certain conditions the momentum of the antenna or the wind may carry the rotator past one of the rotation limit switches, which can damage the limit switches and the position sensing potentiometer. These controllers also allow reversal of direction of rotation while the antenna is in motion. Such a reversal can damage the rotator, the tower, and the antenna. High winds can cause side forces to be applied to the brake wedge of these rotators, preventing them from disengaging. And the analog panel meter, which displays the antenna heading, is not easy to read, particularly quickly, as is sometimes required in radio amateur (ham) contests. More generally, the Cornell-Dubilier controllers require too much operator attention during ham contests. Moreover they are difficult, if not impossible for the handicapped ham, and particularly the blind ham, to use effectively.